1. Field of the Invention
The invention relates to surgical staplers, and more particularly to anvils for use in surgical staplers of the type in which one or more staples are driven through body tissue and against an anvil to form and clinch the staple legs and thereby secure the tissue.
2. Description of the Related Art
Surgical staplers having a wide variety of configurations are known. Generally, the tissue to be secured is positioned between a staple holding assembly and an opposing anvil assembly. One or more generally U-shaped staples are driven from the staple holding assembly, through the tissue, and against the anvil to bend the ends of the staple legs back toward the base of the staple. The formed and clinched staple secures the tissue. Many surgical staplers include staple holding assemblies and anvils configured to drive and form one or more rows of closely spaced staples. In staplers of this general type, it is important that every staple be formed properly since an incompletely or improperly formed staple may leave a gap in a wound closure.
It is conventional to provide separate staple forming pockets for each staple in the staple in the row or rows. It is necessary to maintain relatively stringent alignment between the staple holding assembly and the anvil to assure that the staples enter the pockets correctly for proper clinching. The importance of maintaining good alignment between the relatively movable staple holding assembly and anvil assembly may contribute to the complexity of the instrument and to the cost of manufacturing and maintaining it.
A further complicating factor is presented by the nature of the tissue through which the staples will be driven. Some tissues may include tough or fibrous parts that can deflect the staple legs from their intended path. A deflected staple leg may miss its forming pocket, resulting in a malformed or incompletely clinched staple.
One way to increase the amount of tolerance in a surgical staple and still ensure proper staple leg entry into the forming pockets is to provide an enlarged target area for the staple legs. As shown in FIGS. 1–4, U.S. Pat. No. 5,480,089 discloses a surgical staple forming anvil 100 in which each pocket 102 is provided with channeling surfaces 104 disposed about the distal ends of each leg-forming cup to present an enlarged target area for the staple legs. The channeling surfaces 104 are angled to direct each staple leg toward clinching surfaces 106 at the bottom of the pocket 102. The anvil 100 has a flat upper surface 103 extending between laterally and longitudinally adjacent staple forming pockets 102. The channeling surfaces 104 disclosed in the '089 patent are conical surfaces having an angular orientation θrelative to the upper surface 103 that is smaller than the angular orientation of the staple clinching surfaces 106 at the bottom of the pocket 102.
FIG. 5 illustrates an alternative surgical stapler anvil with a more densely packed array of staple forming pockets. The anvil 200 defines three parallel rows of staggered staple forming pockets 210. Channeling surfaces 204 are provided to enlarge the target area for the staple legs. The lateral width 212 of the staple clinching portion (longitudinally in the center) of each pocket 210 is the same as the lateral width 214 of the leg-receiving portion (at the distal ends of the pocket 210). The anvil 200 of FIG. 5 is configured for use in a surgical stapler which applies three parallel staggered rows of surgical staples while simultaneously cutting the tissue with a blade moving in slot 208. The anvil 200 defines three staggered rows of staple forming pockets along either side of the blade slot 208. Each of the staple forming pockets is principally defined by arcuate clinching surfaces 206 and substantially planar angled guide surfaces 204. The anvil of FIG. 5 replaces the compound curved pocket surfaces illustrated in FIGS. 1–4 with arcuate clinching surfaces 206 that are substantially flat in cross-section and planar guide surfaces 204. The clinching surface 206 extends continuously from a descending leg-receiving end portion of the staple forming pocket to an ascending, centrally located leg-clinching portion of the pocket. The compact pocket array arranged in staggered rows of FIG. 5 leaves no planar anvil surface 202 surrounding or between the pockets. It can be seen that the pockets are arranged in longitudinally aligned rows such that the guiding surfaces of pockets of one row meet the guiding surfaces of pockets in an adjacent row to form a linear ridge 216, separating the rows of pockets from each other.
The compound arcuate channeling surfaces disclosed in the '089 patent, while effective, are difficult to form in a cost-effective manner. The pocket array of FIG. 5 is configured without the difficult to form compound arcuate surfaces. It would be beneficial to provide a surgical stapler anvil having a compact array of staple forming pockets, where each pocket presents an expanded target area for the staple legs. It would also be beneficial if such a compact array of staple forming pockets could be produced by a coining process.
While the prior art pocket arrays illustrated in FIGS. 1–5 have been generally effective, further improvements in function and cost efficient production are possible.